The investigation will concern itself with the physiology and dynamics of myometrial activity and their relationship to the distribution of uteroplacental circulation and the onset of labor in monkeys. Specific attention will be directed toward: (a) the interrelationships of steroid hormones, prostaglandins and catecholamines and (b) certain pharmaceutical agents used in clinical practice to treat pathophysiologic conditions of pregnancy on (1) the demonstrated biorhythms of the uterus during late pregnancy, labor and delivery and (2) the distribution of uterine blood flow to placental and nonplacental sites. Sensors will monitor intrauterine pressure, arterial and venous blood pressure, uterine blood flow, and fetal blood pressure continuously in chronic experimental preparations. Radionuclides will be used to analyze various aspects of placental and nonplacental uterine blood flow. Electronic integration of measured parameters will facilitate evaluation of the studies in an effort to identify and assess some of the factors that control uterine activity and the mechanisms of fetal and maternal uterine homeostasis. A primate breeding colony will be maintained.